Many new communications devices and related services have emerged, to allow people to communicate freely as they roam, without the need for a fixed network connection. In particular, modern digital public wireless telephone networks offer customers a wide range of voice and data communication services combined with a high degree of mobility. In this context, situations arise in which it is desirable to obtain information about the physical or geographic location of a mobile communication terminal and/or its user. For example, some carriers offer services in which the user at the mobile station may request location information and/or information about the surrounding geographic locale, for display on or audio presentation from the mobile station. As another example, some carriers and/or other providers offer location services that allow an authenticated third party to request and obtain the location of a mobile station, for example, so that a parent can obtain information about the location of a child or other relative. Emergency services, such as E911, also requires accuracy regarding the current location of the mobile terminal device.
Increasingly, Global Positioning System (GPS) is used to track the location of a mobile terminal device. The GPS determines the location of an object by using GPS satellites orbiting the earth. As a GPS enabled mobile station has been introduced, and to support such services, a network architecture has been developed that includes a Position Determining Entity (PDE), which communicates with a Mobile Station (MS) having a GPS receiver to determine the location of the MS. To enhance performance beyond that of the GPS receiver in a stand-alone mode, the mobile communication industries have developed Acquisition Assistance (AA), or Assisted GPS. With this approach, the PDE or another node of the wireless communication network provides satellite signal code phase (i.e., signal timing) data to the mobile station. For the PDE to provide the satellite signal code phase data to the mobile station, the MS must first send the pseudo-noise (PN) pilot signal phase offsets of multiple WWAN Base Transceiver Stations (BTSs), which it receives from the WWAN BTSs, to the PDE. The PDE or another node of the wireless communication network helps a mobile station equipped with a GPS receiver to perform the tasks required to make range measurements and position solutions. The PDE or another node of the wireless communication network communicates with the mobile station equipped with the GPS receiver via a wireless link. The Assisted GPS system, consisting of the integrated GPS equipped mobile station and wireless network components, prevents the mobile station from spending precious time on obtaining the satellite almanac data from invisible satellites that sends weak signals, since the PDE provides the mobile station with satellites which is in clear view of the mobile station and sends strong satellite signals enough at that location to reliably demodulate ephemeris data.
Wireless local area network (WLAN) technologies, such as IEEE 802.11, or the like, were originally developed to provide wireless links for data devices, e.g. as a substitute for a wired local area network (LAN) within a premises or campus environment. However, as WLAN capabilities have expanded and multimedia communications have become more common, WLAN service has also come to support many of the services offered in the public sector via the WWAN. Dual mode devices have been developed that operate via a WLAN, when available and operate via a WWAN at other times.
In the meantime, as dual mode mobile stations operable in a Wireless Wide Area Network (WWAN) as well as a Wireless Local Area Network (WLAN) have been introduced, most of application services that are provided in the WWAN area are required to be available in the WLAN area. In case of the GPS service or the Assisted GPS service, when the dual mode mobile station enters into the WLAN area, the GPS signals may be too weak to be used in determining position of the mobile station, since the WLAN area may be in an indoor environment such as inside of a building. Morever, when the WLAN transceiver is turned on in the WLAN area the MS needs to turn off its WWAN transceiver to conserve its battery power. Therefore GPS signals from satellites and RF signals from the WWAN cannot be used for finding the location of the mobile station.
A need exists for a device and a method which enhance position determination performance of mobile stations in the WLAN area.